The current state of art for ionizing radiation-dose measurement in the range of 150 Gy-20 kGy (One Gray (1 Gy) corresponds to radiation absorbed dose equal to energy deposition of 1 Joule/kg. of material, 1 Gy=100 Rad) permits only off-line dose measurement. The currently used standard techniques used in industry are as follows:                1. Sachets containing dyed Perspex (PMMA), which darkens quantitatively when irradiated, and when measured by spectrophotometry yields a precise measure of dose. In another version, a radio chromic film cast from polyvinyl butyral (PVB) resin mixed with proprietary dye is used. Ionizing radiation activates the dye centers and causes a predictable color change that is related to absorbed dose.        2. Blister-packed pellets, which exploit the dose-dependence of paramagnetic resonance of alanine over a wide dose range. When pellets containing amino acid alanine are irradiated, stable free radicals are produced in a concentration, which depends on the exposure. The measured response to microwaves of the pellet placed in magnetic field of a paramagnetic resonance spectrometer is quantitatively related to radiation dose.        
The techniques listed under S. No. 1 and S. No. 2 are off-line measurement techniques and takes about half an hour to use the supplied equipment. They also require heat treatment for stabilization. These are critical limitations on their usage.
Further, these sensors use either the sealed laminate sachets or pellets, whose shape or size cannot be changed, which limits its application at site.
The irradiated pellets are required to be heated in an oven before the response is measured, and also the sachets/films are also subjected to post-irradiation heat treatment for stable response, which is not viable in commerce.
Specifically, the technique listed at S. No. 1 is an intensity based measurement that depends on photo-darkening measured by spectrophotometer. This technique, therefore, requires careful preservation of the irradiated sachets. Similarly, the alanine pellet based method listed at S. No. 2 is also based on concentration of radiation-induced free radicals. Resultantly, both these techniques are sensitive to source misalignment and power fluctuation.
Other techniques used in prior art are very sensitive to temperature (cross sensitivity), have broad resonance features (˜20 nm FWHM) and hence are not suitable for low dose applications (<1 kGy). As a result, they do not provide good accuracy for wavelength dip measurement, amongst other limitations.